Composite disc brake backing plate

ABSTRACT

A brake backing plate is provided in which a non-compressible core material is sandwiched between two sheet metal stampings to make a lightweight, composite brake backing plate. Each of the stampings has a textured face with a plurality of integrally formed piercing members. By rolling or pressing, the piercing members of the textured faces are fully embedded in the core material, and thus lock the stampings and the core material together.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. continuation application under 35 U.S.C.§111(a) claiming priority under 35 U.S.C. §§120 and 365(c) toInternational Application No. PCT/IB2013/002968, filed Nov. 22, 2013,which claims the priority benefit of Canadian Patent Application No.2,798,303, filed Dec. 7, 2012, the contents of which are incorporated byreference herein in their entirety for all intended purposes.

FIELD OF THE INVENTION

The invention relates to backing plates for disc brake pads.

BACKGROUND OF THE INVENTION

Modern vehicle brake systems allow for slowing or stopping movement ofthe vehicle in a controlled manner. A typical automobile or light truckbrake system includes a disc brake assembly for each of the front wheelsand either a drum brake assembly or a disc brake assembly for each ofthe rear wheels. The brake assemblies are simultaneously actuated byhydraulic or pneumatic pressure generated when an operator of thevehicle depresses a brake pedal. The structures of these drum brakeassemblies and disc brake assemblies, and their actuators, are wellknown in the art.

A typical disc brake assembly includes a rotor which is secured to thewheel of the vehicle for rotation therewith. The rotor has a pair ofopposed friction faces which are selectively engaged by portions of acaliper assembly. The caliper assembly is slidably supported by pinssecured to an anchor plate. This anchor plate is in turn secured to anon-rotatable component of the vehicle, such as the suspended wheel hub.A pair of brake pads (or shoes) are disposed in the caliper assembly onopposite sides of the rotor. These brake pads are operatively connectedto one or more hydraulically actuated pistons for movement between anon-braking position, wherein they are spaced apart from the opposedfriction plates of the rotor; and a braking position, wherein they aremoved into frictional engagement with the opposed friction plates of therotor. Depressing the brake pedal causes the piston to urge the brakepads from the non-braking position to the braking position, frictionallyengaging the friction faces to the rotor and thereby slowing or stoppingthe rotation of the associated wheel of the vehicle.

Each brake pad is made up of a relatively thick, substantially planarmetallic body (the backing plate) to which is attached a cake offriction material (typically a molded composite material) in variousways (including adhesive, rivets, and integral molding into holes orraised features in/on the backing plate).

Backing plates for brake pads are typically made of a single piece ofsolid steel. The backing plate distributes the force of the caliperpiston across the brake pad, and thus it has been believed that a singlepiece solid backing plate is necessary to provide sufficient strengthand rigidity. However, such pieces are very heavy, particularly in largetruck applications. This has been a recognized problem in the art.Weight on the sprung or suspended components of a vehicle degrades ridequality and handling, as well as leading to increased fuel consumptionand waste of valuable material. There have been attempts to address theweight issue by making a slightly thinner backing plate that is“thickened” in local areas (typically edge perimeter) by embossing.However, the resulting plates are still quite heavy.

It would be desirable to provide a lighter weight alternative, takingadvantage of other materials' beneficial properties, while maintainingstrength and rigidity.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, a brake backing plate isprovided. To make up the plate, a non-compressible core material issandwiched between a first sheet metal stamping and a second sheet metalstamping. The first sheet metal stamping and the second sheet metalstamping each have a textured face with a plurality of integrally formedpiercing members.

By rolling or pressing, the textured faces of each of the stampingsengage the core material and their piercing members are fully embeddedin the core material. Thus, the piercing members act to lock togetherthe first sheet metal stamping, the second sheet metal stamping and thecore material.

Preferably, at least one of the first sheet metal stamping and thesecond sheet metal stamping is steel.

Preferably, the core material is a lightweight composite material. Inone embodiment, the core material is a friction material.

In certain embodiments, the core material may be a curable material, inwhich case, the first sheet metal stamping and the second sheet metalstamping can be assembled together while the core material is in anuncured or partially cured state, before allowing the core material tocure or finish curing.

The first sheet metal stamping may include a second textured face with aplurality of integrally formed piercing members for attaching to afriction material to form a brake friction pad.

The first sheet metal stamping may include at least one embossment (e.g.to increase the sheet metal stamping stiffness).

Various shapes of piercing members are possible. In one (presentlypreferred) embodiment, the piercing members have a hook shape.

At least some of the piercing members may extend through the corematerial to contact the opposing textured face. These piercing membersmay be clinched by contact with the opposite textured face. Further, thepiercing members may be co-clinched with each other.

In one embodiment, the core material is a fibrous material and thepiercing members engage with and catch on fibers of the fibrousmaterial.

Preferably, the core material is selected to be heat-resistant. The corematerial may also have other benefits—e.g. be weather-resistant, orcorrosion-resistant.

Preferably, the first sheet metal stamping and the second sheet metalstamping are solid, non-perforated sheets, and the piercing members areformed on the surface of the first sheet metal stamping and the secondsheet metal stamping without piercing or perforating through thestamping.

The first sheet metal stamping and the second sheet metal stamping maybe precut to required dimensions for a finished brake backing plateshape prior to assembly with the core material.

Alternatively, at least one of the first sheet metal stamping and thesecond sheet metal stamping may be precut larger than requireddimensions for a finished brake backing plate shape. At least a portionof this excess may be bent to at least partially cover an edge surfaceof the core material after assembly.

In one such embodiment, the brake backing plate shape has abutment ends,and the excess is provided in the form of at least one tab at eachabutment end. This at least one tab is bent to at least partially coverthe core material at the abutment end. This at least one bent tabprovides a substantially smooth and flat abutment surface for the brakebacking plate (e.g. to transfer load and allow sliding movement where itengages the caliper body).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows isometric top and front views of a disc brake pad (priorart).

FIGS. 2-4 are side views showing formation of a sandwich between metalstampings 1, 2 and core material 7.

FIG. 5 is a detail view of one piercing member 5.

FIG. 6 is a perspective view of a portion of array 10 of piercingmembers 5.

FIG. 7 is a top view of stamping 2 prior to assembly with core material7.

FIG. 8 is a side view of a second embodiment of the sandwich havingfriction material 20 attached by a second array 10 of piercing members5.

FIG. 9 is a side view of FIG. 8 shown in partial assembly whereinabutment tab bending process is illustrated.

FIG. 10 is a side view of a third embodiment (similar to that shown inFIG. 8) having multiple stamping layers.

FIG. 11 is a top view of a stamping having embossed areas 20.

FIG. 12 is a cross-sectional view along lines 12-12 of FIG. 11.

FIG. 13 is a top view of a stamping having a radial pattern of embossedareas 21.

FIG. 14 is a detailed view of surface 11 with detail of one embodimentof piercing member 5.

FIG. 15 is a side perspective view of an embodiment of assembly(friction material 20 and a portion of core material 7 removed to showdetail).

FIG. 16 is a side view of FIG. 15 showing abutment tabs.

FIG. 17 is a top perspective view of FIG. 15.

DETAILED DESCRIPTION

As shown in FIG. 1 (in isometric top and front views), the prior artbrake pad is made up of a friction material cake A that is joined to abacking plate B.

The friction material is an ablative material that contacts the rotor inthe course of braking. Friction materials are generally compositematerials, whose components may include metallic, semi-metallic,inorganic (e.g. ceramic) and organic compounds. In some formulations,friction material may include particles, filaments, shavings or fibersdispersed in the material. A pre-form cake of friction material ismolded onto the backing plate using a heat pressure molding systemwhereby the cake flows into and around various features on the backingplate. When cooled, the friction material becomes fully hard and bondedto the backing plate.

Prior art backing plates are solid, typically steel, plates that mayhave holes or other features for retaining friction material. There aremany different shapes of backing plates, but many applications includeabutment ends C, which are used for mounting and alignment in thecaliper bracket.

In the present invention, a lightweight alternative backing plate isprovided. The weight is saved by using relatively thin metal stampingsthat are permanently joined in a sandwich with a lightweight corematerial. The overall laminated structure displays equivalent strengthand rigidity to solid steel backing plates, and accordingly, there is noloss of function for the decrease in weight.

The plate is referred to as a “composite” backing plate by virtue of thefact that it is composed of heterogeneous materials with inferiorproperties on their own, which are enhanced and made superior by virtueof their joining.

FIGS. 2-4 illustrate in general outline the process for forming acomposite backing plate according to the present invention. A first(upper) sheet metal stamping (generally designated 1) and a second(lower) sheet metal stamping (generally designated 2) are placed so asto sandwich between them a lamina of non-compressible core material 7.Each metal stamping has an inward facing textured surface and an outersurface (which may be plain, as shown in FIGS. 2-4 or may have anexposed texture as shown in FIG. 8, 9). On the stamping 1, the textured(inward) face is 12, and the outward face is 11. On stamping 2, thetextured (inward) face is 13, and the outward face is 14. Generallyspeaking, the orientation of the entire sandwich is reversible.

As shown in FIG. 6, the textured faces 12, 13 feature an array 10 ofpiercing members 5.

As shown in FIG. 3, as the stampings 1, 2 are brought together, thepiercing members 5 bite into and begin to penetrate the core material 7.Finally, as shown in FIG. 4, when the flat portions of the texturedsurfaces 12, 13 touch down at the surfaces 15, 16 of thenon-compressible core material 7, the piercing structures have reachedmaximum penetration and by embedment are locked to the core material.

As used herein, “piercing member” describes any type of nail- orpin-like structure (or hooked or barbed structure) raised on the surfaceof a material (for embedding or piercing). The piercing members 5 may beraised from the surface by carving, gouging or scraping an integralprojection from the surface of the material itself. One method offorming such piercing members is described in co-pending Canadian PatentApplication No. 2,778,455, by the present applicants, filed May 29,2012, which is entitled “Bulk Textured Material Sheeting.” Relatedprocesses are also described in Canadian Patent Nos. 1,330,521;1,337,622; or 2,127,339. The foregoing disclosures are incorporatedherein by reference.

The gouging or scraping process may result in a piercing member 5 havinga configuration as shown in FIGS. 5 and 6, where each piercing member 5has an adjacent surface trench 6 from which material has been removed.The piercing member may be somewhat hook-shaped as shown in FIG. 5 (andin FIG. 14, in which the hooks are shown having a tip portion 5 aopposite root portion 5 b), or a more straight upright (e.g. nail-like)member may be provided.

To form each stamping 1, 2, a continuous length of pre-textured material(i.e. having such piercing members already formed) may be stamped intofinished composite plate profiles. Alternatively, precut workpieces maybe textured individually. The second method may be preferred to obtain amore customized outline of piercing members on the surface. Further,prior to assembly in the sandwich, the stampings may undergo otherforming operations, including embossing areas of the stamping (e.g. toprovide additional friction material attachment surfaces, and/or toprovide additional stiffness of the stamping). At this stage, theproperties of the metal stamping are easily controlled. For example, asshown in FIG. 11 (whose cross-sectional view is provided in FIG. 12),embossings 20 may be press-formed on stamping 2. Embossing provides away for the piston's high force to be distributed across the stamping 2(not just in the small central patch struck by the piston). In turn, theentire surface of the brake pad A contacts the rotor to provide maximumbraking performance. FIG. 13 shows another embodiment with a radialpattern of embossing 21 to spread the piston's force in all directions.

In one embodiment, as shown in FIG. 8, a dual-sided metal sheet may beused for at least one of the stampings (i.e. having piercing membertexturing 10 over at least a portion of each surface). This allows forthe formation of the composite backing plate, and also allows for anexposed textured surface on which friction material may be joined. Asshown in FIG. 10, multiple sheets may be sandwiched together with corematerial. Other variations are possible.

The sandwich of material formed by the present method is able to providean extremely stiff and rigid laminate because of the unique lockingeffect of the piercing members. The piercing members want to stay at aright angle to the lamina face. However, the tips of the piercingmembers (being embedded in the core material) are prevented fromconverging, and thus the entire sandwich of material cannot flex orbend. In this way, an exceptionally stiff laminate is created from whatwould otherwise be a relatively flexible sheet of metal (due to therelative thinness). Various types, qualities and grades of metals may beused (e.g. stainless steel, regular steel, aluminum), including cheaperor lower grade metals that might not ordinarily be considered forbacking plate use.

The core material can be any non-compressible (preferably lightweight)material. Such materials may be selected to have specific propertiesbeneficial for brake pad use (e.g. heat resistance (to limit heattransfer), weather-resistance, corrosion-resistance, etc.). Suchmaterials need not be stiff or rigid on their own and may in fact besomewhat brittle. One presently preferred material is friction materialwhich is already tested and has known performance under brakingconditions. Friction material has the additional advantage of beinglightweight for its size.

As a weight comparison, consider the following example of a backingplate:

Core thickness Overall Steel (using friction Overall thickness thicknessmaterial core) weight Standard steel 0.650″ 0.260″ (6.6 mm) n/a 0.656pound backing plate (16.5 mm) (295 gram) Composite 0.650″ 0.040″ (1 mm)0.181″ 0.400 pound backing plate (16.5 mm) and (4.6 mm) (0.182 gram)0.040″ (1 mm)

The sandwich may be rolled or pressed to achieve full embedment of thepiercing members in the core material. Application of heat or pressuremay also be necessary in certain circumstances. Where a two-sided (i.e.2 textured surfaces) stamping is used (e.g. FIGS. 8, 9), the rolling orpressing may be done with very localized application to avoid breakingor crushing the piercing members that are exposed (e.g. the roller mayfollow tracks between rows of piercing members).

The height of the piercing members and the thickness of the corematerial will govern the degree of embedment. In some cases, as shown inFIGS. 15-17, the piercing members may extend only partway into the corematerial. The shape of the piercing members as hooks may aid in thiscase to provide pull-apart resistance. The hook tips may also grip ontofibers, etc. in the core material (e.g. if fibrous material is used—suchas certain formulations of friction material).

Clinching of the tips adds a further increase in pull-apart or peelresistance. As used herein, “clinch” (clinching, clinchable, clinched)describes the act of bending over the exposed tip of a pin- or nail thathas pierced through two or more layers and extends therefrom. Clinchingis a common practice in the wood construction trade. Clinching isanalogous to riveting in metal work, or to any other deformation of afastener to prevent its easy withdrawal. The purpose of clinching is toimpart greater cohesion between the two laminate layers that are sojoined. “Co-clinched” refers to the piercing members interengaging witheach other and with the core material (from above and below) to form afully criss-crossed web of pierced material. In the present case,piercing members may clinch by contact with opposing textured surfacesand may co-clinch by contact with other piercing members.

FIGS. 7 and 9 show a further embodiment in which abutment end covers areformed as a secondary operation. The sandwich by itself leaves exposedstamped metal edges, which may lead to undesirable scraping or drag inthe caliper bracket. To avoid this, a surface of enhanced smoothness andflatness can be provided by using tabs of the metal stamping to coverthe core material at each abutment end. One embodiment is shown in FIG.7, in which a blank of metal is provided with the general outline of thefinished backing plate shape plus tab extensions 2 b-2 d at the abutmentends. These tabs can be bent down (or up) to cover the abutment end andits sides (as shown in FIG. 9), enclosing the core material 7 at theseends. The abutment ends can be submitted to further flattening,grinding, sanding or coating operations to ensure an even smoother,flatter surface. It will also be appreciated that other overhangingportions of the stampings (besides the abutment ends) may also be bentup or down to achieve various effects (including full encasement of allsides of the core material).

The foregoing description illustrates only certain preferred embodimentsof the invention. The invention is not limited to the foregoingexamples. That is, persons skilled in the art will appreciate andunderstand that modifications and variations are, or will be, possibleto utilize and carry out the teachings of the invention describedherein. The scope of the claims should not be limited by the preferredembodiments set forth in the examples, but should be given the broadestpurposive construction consistent with the description as a whole.

1. A brake backing plate comprising: a first sheet metal stamping; asecond sheet metal stamping; a non-compressible core material sandwichedbetween the first sheet metal stamping and the second sheet metalstamping; the first sheet metal stamping and the second sheet metalstamping each having a textured face with a plurality of integrallyformed piercing members, the textured faces of each of the stampingshaving been rolled or pressed into the core material such that thepiercing members are co-clinched with each other via the core material,thus locking the first sheet metal stamping, the second sheet metalstamping and the core material together.
 2. The brake backing plate ofclaim 1, wherein at least one of the first sheet metal stamping and thesecond sheet metal stamping is steel.
 3. The brake backing plate ofclaim 1, wherein the core material is a lightweight composite material.4. The brake backing plate of claim 1, wherein the core material is afriction material.
 5. The brake backing plate of claim 1, wherein thecore material is a curable material, the first sheet metal stamping andthe second sheet metal stamping having been assembled together while thecore material was in an uncured or partially cured state, beforeallowing the core material to cure or finish curing.
 6. The brakebacking plate of claim 1, wherein the first sheet metal stampingincludes a second textured face with a plurality of integrally formedpiercing members for attaching to a friction material to form a brakepad.
 7. The brake backing plate of claim 1, wherein the first sheetmetal stamping includes at least one embossment.
 8. The brake backingplate of claim 1, wherein the piercing members have a hook shape.
 9. Thebrake backing plate of claim 1, wherein at least some of the piercingmembers extend through the core material to contact the opposingtextured face.
 10. The brake backing plate of claim 9, wherein thepiercing members are clinched by contact with the opposing texturedface.
 11. The brake backing plate of claim 9, wherein at least someopposing piercing members are co-clinched with each other.
 12. The brakebacking plate of claim 1, wherein the core material is a fibrousmaterial and the piercing members engage with and catch on fibers of thefibrous material.
 13. The brake backing plate of claim 1, wherein thecore material is selected to be heat-resistant, weather-resistant, orcorrosion-resistant.
 14. The brake backing plate of claim 1, wherein thefirst sheet metal stamping and the second sheet metal stamping aresolid, non-perforated sheets, and the piercing members are formed on thesurface of the first sheet metal stamping and the second sheet metalstamping without piercing or perforating through the stamping.
 15. Thebrake backing plate of claim 1, wherein the first sheet metal stampingand the second sheet metal stamping are precut to required dimensionsfor a finished brake backing plate shape prior to assembly with the corematerial.
 16. The brake backing plate of claim 1, wherein at least oneof the first sheet metal stamping and the second sheet metal stamping isprecut larger than required dimensions for a finished brake backingplate shape, at least a portion of the excess being bent to at leastpartially cover an edge surface of the core material after assembly. 17.The brake backing plate of claim 16, wherein the brake backing plateshape has abutment ends, and the excess is provided in the form of atleast one tab at each abutment end, the at least one tab being bent toat least partially cover the core material at the abutment end.
 18. Thebrake backing plate of claim 17, wherein the bent tab provides asubstantially smooth and flat abutment surface for the brake backingplate.